Tylenol reduces pleasure along with pain, study finds

Contained within more than 600 medicines available in the United States, acetaminophen is the most common drug ingredient in the country, according to the trade group Consumer Healthcare Products Association (CHPA). Every week, nearly a quarter of American adults (about 52 million people) use a medicine containing acetaminophen. It is the primary ingredient in the over-the-counter pain reliever Tylenol.

Acetaminophen performs little miracles when it comes to pain – but it also comes with a number of potential side effects; and one of the reasons why we advocate for using natural remedies instead. But a new study has discovered a side effect that no one quite expected: Participants who took acetaminophen reported less strong emotions – both negative and positive – compared to those who took placebos. It was the first time this effect has been documented, according to a statement for the research.

Previous research has demonstrated that acetaminophen can have an effect on psychological pain, but the new study pushes it further by showing that it also reduces how much users actually feel positive emotions, said Geoffrey Durso, lead author of the study and a doctoral student in social psychology at The Ohio State University.

"This means that using Tylenol or similar products might have broader consequences than previously thought," Durso said. "Rather than just being a pain reliever, acetaminophen can be seen as an all-purpose emotion reliever."

Durso conducted the study with Andrew Luttrell, also from Ohio State, and Baldwin Way, an assistant professor of psychology and the Ohio State Wexner Medical Center's Institute for Behavioral Medicine Research.

Way said that participants had no idea that they were feeling or acting any differently. "Most people probably aren't aware of how their emotions may be impacted when they take acetaminophen," he said.

The study included 82 college students; half took 1000 milligrams of acetaminophen and the other half took an identical-looking placebo. After 60 minutes, the students were shown 40 photographs selected from a database used by international researchers to elicit emotional responses. The images ran the spectrum from abysmal (crying, malnourished children) to neutral (a farm scene) to the very pleasant (kids and cats).

After looking at each picture, the students rated it in terms of how positive or negative the photo was on a scale of -5 (extremely negative) to +5 (extremely positive). They then looked at the same images a second time and rated them on how much the photo made them feel an emotional reaction.

The results showed that the students who took acetaminophen rated all the photographs less extremely than did those who took the placebo. For the participants who took the acetaminophen, positive photos were not seen as brightly, negatively photos were not seen as darkly. The same was true of their emotional reactions.

"People who took acetaminophen didn't feel the same highs or lows as did the people who took placebos," Way said.

At this point, the researchers don't know if other pain relievers such as ibuprofen and aspirin have the same effect, although they plan on investigating the question. In the meantime, should you decide to opt for acetaminophen, don't be surprised if you feel a little flat.